The real work will be in Configuring the second instance to overcome any potential conflict. So, amusing that you already have a running Cognos installation and you need to install another instance of Cognos. Here is how to do this,

1- On the web server ensure that there are separate virtual directories pointing to the corresponding install directory for each instance.

2- In Cognos Configuration under Environment, ensure that no two instances are both set to use the same port number (9300 for the default Tomcat application server) in the Dispatcher URIs for gateway, External Dispatcher URI, Internal Dispatcher URI, Content Manager URIs and Dispatcher URIs for external applications settings. (I used 9301 for the second installation).

3- In Cognos Configuration under Environment -> Logging, ensure that no two instances are both set to use the same Local log server port number ( 9362 was the default port used in the first installation, I used 9363 for the second installation).

4- In Cognos Configuration under Environment -> Cognos 8 service ensure that no two instances are both set to use the same Shutdown port number. ( 9399 was the default port used in the first installation, I used 9398 for the second installation).

5- Ensure that no two instances are pointing to the same content store. In Cognos Configuration under Environment -> Cognos Content database ensure that no two instances are both set to use the same Shutdown port number. ( 1527 was the default port used in the first installation, I used 1528 for the second installation). You will need to change the same port under the Data Access -> Content Manager -> Cognos Content Store.

Note : Make sure any new port assigned are not currently in use. You can run “netstat -a” to list out all the port numbers currently in use.